Improper validation of certificate with host mismatch in cURL - CVE-2026-9547

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Main Vulnerability Database Vulnerabilities #VU135089

Improper validation of certificate with host mismatch in cURL - CVE-2026-9547

Published: June 24, 2026


Vulnerability identifier: #VU135089
CSH Severity: Medium
CVSS v4: 6.3 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-9547
CWE-ID: CWE-297
Exploitation vector: Remote access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a remote attacker to perform a man-in-the-middle attack.

The vulnerability exists due to improper validation of certificate with host mismatch in the CURLOPT_SSH_KEYFUNCTION callback when validating SSH host keys for SCP:// or SFTP:// transfers. A remote attacker can present a host key type that does not match the key type already recorded for the host in the known_hosts file to perform a man-in-the-middle attack.

Only libcurl-based applications built with the libssh backend and using the callback are vulnerable. The curl command line tool is not affected.


Affected software

cURL
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 12 SP5 LTSS Extended
SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise High Performance Computing 12
SUSE Linux Enterprise Server 12
SUSE Linux Enterprise Server for SAP Applications 12
SUSE Linux Enterprise Real Time 15
SUSE Manager Retail Branch Server
SUSE Manager Proxy
SUSE Manager Server
SUSE Linux Enterprise Micro for Rancher
SUSE Linux Enterprise Micro
Red Hat Enterprise Linux for x86_64 - Extended Update Support
Red Hat Enterprise Linux for IBM z Systems - Extended Update Support
Red Hat Enterprise Linux for Power, little endian - Extended Update Support
Red Hat Enterprise Linux for ARM 64 - Extended Update Support
Ubuntu
Basesystem Module
openSUSE Leap
openEuler
Anolis OS
Fedora
LANTIME Operating System Firmware (LTOS)
curl (Ubuntu package)
libcurl-devel
curl
curl-debuginfo
curl-debugsource
libcurl
curl-help
libcurl4-32bit
libcurl4
libcurl4-debuginfo-32bit
libcurl4-debuginfo
curl-minimal
libcurl-minimal
curl-doc
curl (Red Hat package)
libcurl-devel-64bit
libcurl4-64bit-debuginfo
libcurl4-32bit-debuginfo
curl-mini-debugsource
libcurl-mini4-debuginfo
libcurl4-64bit
curl-fish-completion
libcurl-devel-doc
curl-zsh-completion
libcurl-devel-32bit
libcurl-mini4

How to mitigate CVE-2026-9547

Install security update from vendor's website.

cURL - update to 8.21.0
LANTIME Operating System Firmware (LTOS) - update to 7.10.013
curl (Ubuntu package) - addressed in versions 7.35.0-1ubuntu2.20+esm20, 7.35.0-1ubuntu2.20+esm23, 7.47.0-1ubuntu2.19+esm16, 7.58.0-2ubuntu3.24+esm9, 7.68.0-1ubuntu2.25+esm4, 7.81.0-1ubuntu1.25, 8.5.0-2ubuntu10.10, 8.14.1-2ubuntu1.4, 8.18.0-1ubuntu2.2
libcurl-devel - addressed in versions 7.71.1-52, 7.79.1-53, 8.4.0-35
curl - addressed in versions 7.71.1-52, 7.79.1-53, 8.4.0-35
curl-debuginfo - addressed in versions 7.71.1-52, 7.79.1-53, 8.4.0-35
curl-debugsource - addressed in versions 7.71.1-52, 7.79.1-53, 8.4.0-35
libcurl - addressed in versions 7.71.1-52, 7.79.1-53, 8.4.0-35
curl-help - addressed in versions 7.71.1-52, 7.79.1-53, 8.4.0-35
libcurl4-32bit - addressed in versions 8.0.1-11.126.1, 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1, 8.14.1-150700.7.20.1
curl-debuginfo - addressed in versions 8.0.1-11.126.1, 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1, 8.14.1-150700.7.20.1
libcurl4 - addressed in versions 8.0.1-11.126.1, 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1, 8.14.1-150700.7.20.1
libcurl4-debuginfo-32bit - update to 8.0.1-11.126.1
libcurl-devel - addressed in versions 8.0.1-11.126.1, 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1, 8.14.1-150700.7.20.1
curl - addressed in versions 8.0.1-11.126.1, 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1, 8.14.1-150700.7.20.1
curl-debugsource - addressed in versions 8.0.1-11.126.1, 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1, 8.14.1-150700.7.20.1
libcurl4-debuginfo - addressed in versions 8.0.1-11.126.1, 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1, 8.14.1-150700.7.20.1
curl - update to 8.4.0-24
libcurl - update to 8.4.0-24
libcurl-devel - update to 8.4.0-24
curl-minimal - update to 8.4.0-24
libcurl-minimal - update to 8.4.0-24
curl-doc - update to 8.4.0-24
curl (Red Hat package) - update to 8.12.1-1.el10_0.10
libcurl-devel-64bit - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1
libcurl4-64bit-debuginfo - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1
libcurl4-32bit-debuginfo - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1, 8.14.1-150700.7.20.1
curl-mini-debugsource - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1
libcurl-mini4-debuginfo - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1
libcurl4-64bit - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1
curl-fish-completion - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1
libcurl-devel-doc - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1
curl-zsh-completion - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1
libcurl-devel-32bit - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1
libcurl-mini4 - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1
curl - addressed in versions 8.15.0-8.fc43, 8.18.0-8.fc44

External References

Related Security Bulletins